Cap for a writing instrument



FIG. 1 is a perspective view of a cap for writing instrument showing my new design;

FIG. 2 is a front view thereof;

FIG. 3 is a bottom view thereof;

FIG. 4 is a rear view thereof;

FIG. 5 is a left side view thereof; and,

FIG. 6 is a right side view thereof.

The broken line showing of the inside of the cap in FIG. 6 is for the purpose of illustrating interior portions of the cap and forms no part of the claimed design. 

The ornamental design for a cap for a writing instrument, as shown and described. 